Heating and sealing head for packaging machines of products in trays

Abstract

A heating and sealing head ( 1 ) for packaging machines (M 1 ; M 2 ; M 3 ) of products in trays (V), comprising a fixed support group ( 2 ) provided with first actuation means ( 3 ) electrically connected to a pneumatic system ( 4 ) for delivering compressed air, and a mobile application group ( 5 ) mechanically coupled to the fixed support group ( 2 ) by means of first fixing means and comprising heating means ( 6 ) electrically connected to an electric current generator ( 7 ), preferably alternating, which activates the heating means ( 6 ) to produce heat useful for sealing a closing and packaging film to one or more trays for containing products when the trays themselves are arranged under the heating and sealing head ( 1 ) in a packaging machine (M 1 ; M 2 ; M 3 ). In particular, the heating means ( 6 ) comprise an electromagnetic inductor body ( 8 ) which produces the heat due to the effect of the parasitic electric currents induced by a magnetic field generated by the electromagnetic inductor body ( 8 ) when crossed or affected by the electric current.

The invention claimed is: 
     
       1. Heating and sealing head for packaging machines (M 1 , M 2 ; M 3 ) of products in trays (V), comprising:
 a fixed support group provided with actuation means operatively connected to a pneumatic system for delivering compressed air; 
 a mobile application group, mechanically coupled to said fixed support group through first fixing means and comprising heating means electrically connected to an electric current generator which activates said heating means to produce heat useful for sealing a closing and packaging film to one or more trays for containing products when said trays are arranged under said heating and sealing head in a packaging machine, 
 wherein said heating means comprise at least one electromagnetic inductor body which produces said heat due to the effect of the parasitic electric currents induced by a magnetic field generated by said electromagnetic inductor body when crossed or affected by said electric current supplied by said electric current generator, 
 wherein said mobile application group comprises an intermediate heat storage plate directly facing and separated from said electromagnetic inductor body and made at least at a surface layer made of ferromagnetic material adapted to accumulate said heat produced by said electromagnetic inductor body. 
 
     
     
       2. Head according to  claim 1 , wherein said electromagnetic inductor body is contained in a box-shaped element belonging to said fixed support group. 
     
     
       3. Head according to  claim 1 , wherein said electromagnetic inductor body is fixed to the bottom wall of a box-shaped element belonging to said fixed support group. 
     
     
       4. Head according to  claim 1 , wherein said electromagnetic inductor body includes a composite assembly of the sandwich type consisting of:
 a first laminar layer made of thermally and electrically insulating material; 
 a second laminar layer made of thermally and electrically insulating material and parallelly spaced apart from said first laminar layer by a prefixed distance; 
 a plurality of reels made of conductive material, interposed between said first layer and said second layer and electrically connected to said electric current generator. 
 
     
     
       5. Head according to  claim 4 , wherein said first layer and said second layer of said composite assembly are made of the same thermally and electrically insulating material and said thermally and electrically insulating material consists of mica. 
     
     
       6. Head according to  claim 1 , wherein said ferromagnetic material is any of the materials selected from the group consisting of stainless steel, nickel, cobalt, one of the transition metals and/or combinations thereof. 
     
     
       7. Head according to  claim 1 , wherein said mobile application group comprises a laminar thermal welding plate made of a thermally conductive material, parallel and coaxially arranged, facing and spaced apart with respect to said intermediate heat storage plate to which it is coupled by means of second fixing means, such that said laminar welding plate has an upper face directly facing a lower face of said intermediate heat storage plate, from which it is separated by an inner air chamber. 
     
     
       8. Head according to  claim 7 , wherein said thermally conductive material of said laminar thermal welding plate is aluminum. 
     
     
       9. Head according to  claim 7 , wherein said mobile application group comprises a locking plate adapted to be arranged close to said closing and packaging film and having an upper face directly facing a lower face of said laminar thermal welding plate and one or more through holes in each of which a raised annular rib is engaged which protrudes from said lower face of said laminar thermal welding plate and from said locking plate and is adapted to receive one of said trays to be packaged. 
     
     
       10. Head according to  claim 9 , wherein said mobile application group includes a laser pyrometer adapted to measure and control the temperature of said laminar thermal welding plate, arranged on the external surface of a perimeter frame of said mobile application group. 
     
     
       11. Head according to  claim 10 , wherein said actuation means comprise a plurality of pneumatic linear actuators each of which operatively connected to said pneumatic system, adapted to move said mobile application group with respect to said fixed support group along an axial coupling direction between said mobile application group and said fixed support group so as to arrange said raised annular rib of said laminar thermal welding plate close to each of said underlying trays to be packaged for the time needed to apply by sealing said closing and packaging film to said trays by means of said heat transferred to said laminar thermal welding plate. 
     
     
       12. Head according to  claim 1 , wherein said mobile application group is removably coupled to said fixed support group. 
     
     
       13. Head according to  claim 1 , wherein said first fixing means comprise any one of the mechanical coupling systems such as to allow the stable but removable coupling of said mobile application group to said fixed support assembly, and they are provided with at least one operating knob which can be operated by an operator to alternately arrange said first fixing means in the operating position, in which they stably couple said mobile application group to said fixed support group, and in the release position, in which they uncouple said mobile application group from said fixed support group to allow maintenance and/or format change operations of said mobile application group according to the number and/or format of said trays to be packaged. 
     
     
       14. Head according to  claim 1 , wherein said mobile application group is at least partially contained in the overall dimensions of said fixed support group from which it is caused to at least partially protrude by means of said actuation means during the sealing step of said closing and packaging film to said underlying trays. 
     
     
       15. Head according to  claim 1 , wherein said pneumatic system and said electric current generator are electrically connected to a central processing and control unit available to an operator by means of a control panel.